No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 583 
ever, in his later publication (No. 125, p. 471), questions the 
correctness of his earlier determinations, and states positively 
that, in Sphyrna malleus, Prionodon glaucus, Scyllium canicula, 
and Galeus canis, that part of the muscle that lies immediately 
behind the angle of the chin is innervated by the trigeminus, 
and hence belongs to the mandibular arch. The nerve by 
which this small anterior portion of the muscle is innervated 
is said by Vetter to be a branch of the r. maxillaris inferior 
trigemini, given off close to the symphysis of the mandible. 
It runs backward and inward over the cartilage into the 
muscle, and there forms numerous anastomoses with the deli- 
cate terminal branches of the r. hyoideus facialis. In the 
American Galeus canis I could not with certainty identify this 
nerve. In the specimen examined of that fish a branch was 
given off by the r. maxillaris inferior trigemini while that 
nerve still lay on the outer surface of the adductor mandi- 
bulae, at some little distance from the end of the muscle, and 
hence at a still greater distance from the symphysis of the 
mandible. The branch ran medianward along the outer surface 
of the adductor, and, crossing the narrow line of cartilage which 
alone separates the adductor from the ventral constrictor, entered 
the latter muscle at some distance from its front end. It seems 
hardly possible that this can be the branch described by Vetter, 
but it seems still less possible that in this careful work he could 
have failed entirely to find so large a nerve. In Carcharinus 
the corresponding branch was a large and important one given 
off before the main nerve reached the outer surface of the 
adductor. It separated into two fairly equal portions before 
reaching the constrictor, one of which ran forward and the other 
backward in that muscle. A small branch was sent backward 
and medianward from, or from near, the base of the nerve. In 
both Galeus and Carcharinus the main inferior maxillary, after 
leaving the adductor at its front end, continued forward along 
the outer surface of the cartilage of the lower jaw toward the 
symphysis, giving off several branches. One of these branches 
may be the one described by Vetter as going to the extreme 
front end of the constrictor. I did not so find it, but I did not 
make careful search, and cannot say that it does not exist. If 
